If others are like me, I only spend my money on technology I need. I'll let other people spend their money on technology for technology's sake. My brother-in-law always buys the latest gadget because he loves having the latest and greatest. That makes him feel good, fine with me. I'm using one of my kids' Razr phones when they were done with it because I don't need or want anything more than that. I'm old enough to know you can easily live without all that other crap. Mobile voice and the occasional text is all I desire.

The high cost of broadband has been one of the key factors to affect the proliferation of any kind of packet switching service. Long term contract is one of the example. The dollar per Mbps is another. On the other hands, US is a huge country. To wire every household to offer decent data rate has always been a challenge to carrier. Wireless could be an answer to some region. We have to remember at some point the packet traveling through wireless has to come down to wired in order to be delivered.
In Europe, people use to have multiple mobile phones in order to, for example, drive down the cost. I am not sure whether it is still the case. If it is, certain segment of the market would be the primary contributor to the overall high percentage of adoption.

Just a point of clarification. I'm not sure what people mean by "IPTV." The more accepted use is something that emulates a cable TV system, but uses Internet Protocols. E.g, AT&T U-verse. In schemes like this, sure enough, you have to pay a monthly ransom.
But if people mean Internet TV, it all depends what Internet portals you get the TV content from. There is quite a lot of ad-supported TV content available over the Internet, which allows Internet TV to be a one-time outlay just like owning a tablet or using over the air TV. Well, almost. Just like with tablets, you still have to pay for your broadband link.

For me and other engineers I know it's about the price. Every US telecom carrier nickle and dimes us for every added option, it seems that it is like buying a car with the telecom carriers in the US. For instance I will never buy a new car simply because of the following experience, the salesman asks me, do you want floor mats, well that's an extra 100 dollars, oh you want bumpers that's an extra 1000 dollars well the phone carriers in the US use the same tactics but in my experience they are worse than car salesmen.
Minutes, seconds milliseconds, in the smallest increments if they can then they will charge you extra for everything and the Feds let em get away with it. Forget about a smartphone when you have to worry about close to a 200 dollar a month bill for a family and getting locked into 5 year contracts. Sometimes I dream about having 2 paper cups and miles of string or a CB radio network, the sound quality would certainly be 1000 of times better than the crap digital voice that we now have.

It's shocking that the US cellphone market is so fragmented, which, rather than promoting competition results in captive segments that don't really compete.
How many incompatible systems do we have? 3? 4? I lost track---and to top it off, they all are incompatible with the worldwide GSM network. At least the LTE is supposed to be a worldwide standard---or is it? Maybe a day will come when the cell towers won't have those multi-story antenna arrangements to serve all the existing systems.

I think it's a shame they don't separate out the three proucts, because I see a significant difference between smart-phones/IPTV and tablets:
A tablet is simply a one-off purchase: you buy it and then you use it with no more significant outlay.
The market penetration of smart-phones, however, depends on how competitive the phone market is. It get the impression, for example, that the competition is poor in the US mobile phone market, hence prices are higher, hence less samrtphone penetration. (I don't give a monkey's what the other guy thinks - a smart phone is one hell of a useful device. Mine costs me about $22 a month, including more calls and texts that I use and unlimited data; my impression is that prices in the use are higher than that).
Likewise, the market penetration of IPTV depends on how competitive the broadband market is and how competitive the conventional TV market is. If convention TV is good and/or broadband is expensive, the market penetration of IPTV will be lower.
So, I think it would be very interesting to see the Tablet figures in isolation.

I would offer another possibility. The smartphone penetration of 35 percent for the US, vs 70 percent for Sweden, tells me that the US is about where one would expect it to be for this type of device, whereas Sweden is way beyond what would appear to be even reasonable.
One thing might simply be, Americans care a little bit less about what the other guy thinks? There's plenty of poseur posturing going on everywhere, don't get me wrong, however in my experience, it is a tad lower in the US than it might be in Western Europe or Japan.